Detectives said George Robson created a "climate of fear" at Banham Marshalls College in Norfolk, during the 1970s and '80s.
Pupils were made to settle differences with "staged fights", beaten with a studded belt, force fed - with one victim saying he was made to eat his own vomit - and thrown into a freezing pond. A seven-year-old boy was also forced to smash a favourite toy with a hammer as punishment for causing minor damage to a locker, detectives said.
Robson, 66, was convicted of cruelty alongside two other staff members: his brother Anthony, 63, the school's head of care, and David Clarke, 56, its former warden.
Banham Marshalls, originally known as the Old Rectory, is now under new ownership and operates under a different name.
Detectives launched an inquiry four years ago after former pupils came forward to complain about the way they had been treated. They investigated hundreds of allegations of cruelty against children aged between seven and 16.
Detective Inspector Matt Sharman, who led the inquiry, said: "The school was clearly run in a climate of fear, with control of children of paramount importance.
"Even in the days when corporal punishment was still legal, events at the school went far beyond what was acceptable.
"The many victims in the case, some of whom have never come to terms with what happened to them, were traced to addresses all over this country and even abroad."
A former houseparent - Leslie Beckett of Harleston in Norfolk - was accused of indecently assaulting pupils. But he died before he could stand trial.